Jutoh (http://www.jutoh.com/) is the only tool I use for ebook compiling. It’s very, very simple to go from a document in Word format (whether output from Word itself, from Google Docs, Scrivener or whatever) to an ebook and, in this video, I show how to create a standard .mobi for uploading to Amazon KDP Select (the process is identical for epub). As I say at the end, I can go from .docx -> .mobi in less than a minute.
There are a couple of settings you need to be careful to get right, though – they’re covered in the video and also below. If you’ve ever watched other Jutoh tutorials, you might notice that the horrible blue titles from Word get carried through to the epub – this is how to stop that.
Get these settings right!